This invention relates to electrophotographic reproducing apparatus and more particularly, to a document exposure system which provides edge fadeout.
The most common type of electrophotographic reproducing apparatus comprises a transparent platen which supports a document to be reproduced. A scanning optics system including a reciprocating illumination source and first mirror projects a light pattern onto a photosensitive surface having a uniform electrostatic charge thereon thereby discharging the photosensitive surface in accordance with the light pattern resulting in a latent electrostatic image remaining on the surface which is subsequently rendered visible by development with electroscopic marking particles, commonly known in the art as toner.
In most if not all prior art machines a thick document edge together with the relative position of the illumination source produces a shadow along the edge of the document which shadow results in an objectionable dark border or edge on the copy substrate.
Furthermore, if the copy paper size corresponds to the area of the photosensitive member containing the latent image and if the copy paper and image are properly registered than the phenomenon known as border or edge development does not occur. However, it frequently happens that the foregoing is not the case and the border or edge areas are developed with subsequent transfer to result in objectionable copies.
A number of approaches to solve the foregoing problems of edge or border development have been provided for example, the underside of the platen cover of such a machine has been made into or provided with a diffuse reflector as disclosed in U.S. Pat. No. 3,642,371. With such an arrangement portions of the reflector which extend beyond the document act to reflect illumination onto the photosensitive member beyond a predetermined area thereon corresponding to the image area thereby discharging those portions such that they do not get developed.
Another arrangement which provides for edge fadeout, as disclosed in U.S. Pat. No. 3,788,737,comprises an illumination device forming a part of the platen cover thereby providing a source of illumination disposed beyond the borders of the document which illumination serves to discharge the photosensitive member adjacent the areas corresponding to the image area.
It is the primary object of this invention to provide an improved scanning optics system for an electrophotographic reproducing apparatus.